DESCRIPTION

SSL_CTX_set_info_callback() sets the callback function, that can be used to
obtain state information for SSL objects created from ctx during connection
setup and use. The setting for ctx is overridden from the setting for
a specific SSL object, if specified.
When callback is NULL, not callback function is used.

SSL_set_info_callback() sets the callback function, that can be used to
obtain state information for ssl during connection setup and use.
When callback is NULL, the callback setting currently valid for
ctx is used.

SSL_CTX_get_info_callback() returns a pointer to the currently set information
callback function for ctx.

SSL_get_info_callback() returns a pointer to the currently set information
callback function for ssl.

NOTES

When setting up a connection and during use, it is possible to obtain state
information from the SSL/TLS engine. When set, an information callback function
is called whenever the state changes, an alert appears, or an error occurs.

The callback function is called as callback(SSL *ssl, int where, int ret).
The where argument specifies information about where (in which context)
the callback function was called. If ret is 0, an error condition occurred.
If an alert is handled, SSL_CB_ALERT is set and ret specifies the alert
information.

where is a bitmask made up of the following bits:

SSL_CB_LOOP

Callback has been called to indicate state change inside a loop.

SSL_CB_EXIT

Callback has been called to indicate error exit of a handshake function.
(May be soft error with retry option for non-blocking setups.)

SSL_CB_READ

Callback has been called during read operation.

SSL_CB_WRITE

Callback has been called during write operation.

SSL_CB_ALERT

Callback has been called due to an alert being sent or received.

SSL_CB_READ_ALERT (SSL_CB_ALERT|SSL_CB_READ)

SSL_CB_WRITE_ALERT (SSL_CB_ALERT|SSL_CB_WRITE)

SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT|SSL_CB_LOOP)

SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT|SSL_CB_EXIT)

SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT|SSL_CB_LOOP)

SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT|SSL_CB_EXIT)

SSL_CB_HANDSHAKE_START

Callback has been called because a new handshake is started.

SSL_CB_HANDSHAKE_DONE 0x20

Callback has been called because a handshake is finished.

The current state information can be obtained using the
SSL_state_string(3) family of functions.